1. Field of the Invention
The present invention relates to a method for calculating a condition for connecting electronic parts typified by semiconductor devices on electronic circuit boards.
2. Description of the Related Art
When an electronic part is mounted and connected to a circuit board by solder bumps as shown in FIG. 7, a temperature profile for soldering has conventionally been decided by considering thermal shock on the electronic part and solderability, such as wetting (Shuji Nakata: Microsoldering in Future, Kogyo Chosakai Publishing Co., 1991, pp. 174–179).
Besides, there are various types of reflow equipment, and the connection condition differs with the size of an electronic part and a circuit board to be joined together.
The connection condition, in other words, the heating condition is decided chiefly by the wettability of solder and the heat-resistance temperature of the electronic part.
A typical reflow condition is shown in FIG. 1 and the area above 220° C. of the graph in FIG. 1 is shown in FIG. 2.